Camshaft,pattern,and method of making



May 20, 1969 K. E. KUENY CAMSHAFT PATTERN, AND METHOD OF MAKING Sheet of 3 Filed Jan. 30, 1967 l NVEN TOR. [fl/M577 .5. KZ/EI/V BY W May 20, 1969 K. E. KUENY I CAMSHAFT PATTERN, AND METHOD OF MAKING Sheet & of 3 Filed Jan. 30, 1967 magi INVENIOR. 4450416254 6. {MFA/V BY Q4, W

N1 sb 74,914 Qua y 0, 1969 K. E. KUENY 3,444,759

CAMSHAFT PATTERN, AND METHOD OF MAKING Filed Jan. 30, 1967 Sheet 3 of 3 is I United States Patent U.S. Cl. 74567 Claims ABSTRACT OF THE DISCLOSURE An inproved camshaft and a novel method and pattern for forming an improved camshaft with generally uniform metallurgical structure and hardness in all of the cam lobes, particularly in the noses and ramps where it normally varies considerably, by overcoming (a) the variable chilling efliect of the mold sections with respect to their spacing from the gate, (b) the variable chilling action of the portions formed in the cope with respect to those formed in the drag, and (c) the variable beat retention of mold sections adjacent bearing journal mold sections with respect to those not so adjacent. This improvement is achieved by using a special pattern to form narrow ravines in the mold, projecting from the mold portions that form the cam lobe noses, such ravines being only in planes parallel to, coplanar with, or perpendicular to the cope and drag junction plane, to form a camshaft having lobe noses with special chilling projections that create like acicular carbide formation in i the several cam lobe nose zones.

Background This invention relates to a novel camshaft, a method of founding camshafts, and novel camshaft mold patterns, and more particularly to such for founding camshafts having generally uniform metallurgical structure and hardness in the several cam lobes, particularly in the nose zones that include the noses and adjacent ramps.

Camshafts are conventionally formed by pouring hardenable iron into a mold, cooling, and heat treating. The hardenability of the casting with heat treating, and consequent wearability, depends upon the metallurgical structure of the cooled casting, as is well known.

The several lobes, specifically the nose and ramp portions of conventional camshafts have substantially varying structures, hardness and wearability. During operation in an engine, some lobe noses and ramps become severely worn where others are only slightly worn. When one or more lobes becomes severely worn, the entire camshaft requires replacement. This problem is particularly acute with respect to the lobes formed near the mold gate, and the lobes adjacent the first bearing journals.

Evaluation and analysis of such camshafts have shown that the nose and ramp portions of cam lobes on the same camshaft normally vary several points on the Rockwell C hardness scale, and also the cam lobe nose structures vary from a completely cellular carbide structure to partially acicular carbide structure, and none is really as hard as desired. Yet, the industry has had to bear this deficiency because it is simply a fact that results with the present founding of camshafts.

Summary of the invention It is an object of this invention to provide a method of founding an improved camshaft having generally uniform metallurgical structure in the several cam lobes on the shaft, particularly in the noses and ramps, each having excellent hardness and wearability, superior to the best cam lobes formed according to the prior art teachings,

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and moreover, with all having generally uniform hardness, regardless of their position in the mold, on the shaft, and whether formed in the cope or drag.

This is achieved 'by overcoming the preheating effect of the nose and ramp portions of the lobe-forming-cavities closest to the mold gate, by overcoming the effect of large metal masses in the bearing journals on the cooling rates of adjacent cam lobes, and by overcoming the differential cooling action of the cope and drag mold members on the cam'noses formed in these respective members. These three normally uncontrolled variables are overcome by uniformly chilling the metal in the cam lobe nose zones, including the noses and ramps, in a special manner that efiectuates like, concentrated acicular carbide formation in all of the nose zones. The undesired effects are overcome by forming into the nose forming portions of the mold cavities, narrow ravines projecting away from the cavities into the mold, to thereby form instantly solidified, white metal, heat radiating fins or pins that throw a uniform controlled chill, with consequent acicular carbide formation, back into all of the lobe noses and adjacent ramps, regardless of where on the shaft the lobe is being formed, and regardless of whether the lobe nose is formed in the cope or drag of the mold. The fins or pins on the pattern and resulting camshaft radiate either parallel to, coplanar with, or normal to the junction plane of the cope-forming-pattern and drag-formingpattern and to the junction plane of the resulting mold cope and drag.

Other objects and advantages of the method will become apparent upon studying the following disclosure in conjunction with the drawings.

Brief description of the drawings FIG. 1 is a perspective view of the novel camshaft casting;

FIG. 2 is a sectional view showing cam lobe No. 4, taken on plane IIII of FIG. 1;

FIG. 3 is a sectional View showing lobe No. 7, taken on plane III-III of FIG. 1;

FIG. 4 is a sectional view showing cam lobe No. 16, taken on plane IVIV of FIG. 1;

FIG. 5 is a fragmentary perspective view of a novel drag-forming pattern;

FIG. 6 is a fragmentary perspective view of a novel cope-forming pattern;

FIG. 7 is an enlarged perspective view of portion VII of the pattern in FIG. 6;

FIG. 8 is a fragmentary enlarged perspective view of portion VIII of the pattern in FIG. 5;

FIG. 9 is a perspective view of .a single cam lobe with a fin of the type illustrated with respect to FIGS. 1 through 8;

FIG. 10 is a perspective view of a single cam lobe with a plurality of pins illustrating a second form of structure within the broader aspects of the concepts herein;

FIG. 11 is a perspective view of a single cam lobe showing a plurality of transverse fins illustrating a third form of the invention within the broader concepts herein; and

FIG. 12 is a side elevational view of the cam lobe and transverse fins in FIG. 11.

Detailed description of the preferred embodiments of the invention Referring now to FIG. 1, the camshaft casting 10- there illustrated includes a central shaft 12 having integral hearing journals 14 at spaced intervals therealong, and a plurality of spaced cam lobes 18 between the bearing journals, with the illustrative camshaft having sixteen of such cam lobes. Obviously, the number of cam lobes employed will vary directly with the number of cylinders in the engine involved, the illustrated camshaft being made to accommodate an eight cylinder engine, with eight cam lobes for operating the intake valves, and eight cam lobes for operating the exhaust valves. For convenience, the cam lobes are numbered beginning with the end of the camshaft into which the metal is first poured into the corresponding mold through a gate.

The mold includes a drag and a cope, with the drag being formed by the drag pattern 50 in FIG. 5, and the cope being formed by the cope pattern 52 in FIG. 6. The drag and cope patterns form mating drag and cope mold elements which fit together on a junction plane that leaves a tell-tale junction mark 17 along the length of the casting, and which is clearly visible prior to machining of the casting. This mark 17, on opposite sides of the casting, is therefore in a single plane.

Camshafts made according to conventional prior art methods are of course also cast in a mold made up of a drag and cope, formed from a drag forming pattern and a cope forming pattern generally similar to, but having a distinct difference from those shown in FIGS. 5 and 6, as explained hereinafter. According to the conventional method, when the molten hardenable iron is poured into the gate at one end of the mold, it fiows through the mold to the opposite end, with pouring being continued until the mold is filled. Normally, several like camshafts will be cast in the same unitary mold assembly. However, for

purposes of convenience, the description of this invention will be made with respect to the formation of one camshaft. When this conventional camshaft is thus formed, the resulting casting has a substantial range of hardness between the nose zones of the several cam lobes formed integral with the shaft. That is, the cam lobes on the far end, spaced from the gate, will normally be substantially harder than those adjacent the gate. Further, those spaced from the bearing journals will be of greater hardness than those immediately adjacent the bearing journals. Moreover, those having the cam noses formed in the lower drag portion of the mold will be of greater hardness than the cam lobe noses formed in the upper cope portion of the mold.

These three variables are generally of an uncontrollable nature, so that the resulting camshaft will typically have cam lobe noses that will vary between a hardness of Rockwell C 50-52 for the nose zones of the first cam lobes near the gate, to a hardness of Rockwell C 57 for the last cam lobe nose on the end opposite the gate. This variation in hardness is substantial, causing the lobe nose zones, particularly the nose itself and the adjacent ramps, to wear considerably on two or three cam lobes when very little Wear has occurred on others. This inability to cause all of the cam lobes to be of the desired higher hardness necessitates replacement of the camshaft when the softer cam lobes become unduly worn.

Analysis shows this variation in hardness, and absence of uniform hardness to be due to the three factors noted above. More specifically, the cam lobes nearest the molten metal inlet gate tend to be softer because of the slower cooling thereof resulting with the preheating action of this area of the mold as the molten metal flows continuously through it to the other end of the mold cavity. Secondly, the cam lobes formed adjacent the bearing journals cool more slowly because of the large mass of heated metal in the bearing journals themselves, which tends to heat the zone of the mold adjacent thereto. Further, the cam lobes having their nose zones in the upper cope element of the mold have a hardness less than those formed in the drag since the first metal into the cavity drops into the nose zones in the drag and chill rapidly in the as yet cool mold, whereas the entire mold is heated substantially above its initial temperature by the time the molten metal fills the nose zone cavities in the upper cope member. As a result of these three factors, the several cam lobes will be of considerably varying hardness depending upon whet-her each is influenced by one, two or three of these noted factors. When all three conditions occur on a particular cam lobe, that particular cam lobe will generally have the softest nose zone. It therefore will be the first to wear rapidly, and will largely determine the life of the camshaft in an engine.

This invention overcomes the adverse characteristics of these three factors by causing practically uniform chilling of the nose zones, including the nose and the ramps, of the cam lobes all along the length of the shaft. Hence, the nose Zones have practically uniform hardness along the length of the shaft, no matter where the cam lobe happens to be, and furthermore, the hardness of all of them is greater than the best cam lobe of the prior art. More specifically, according to the new method, the nose zones of the most favorably positioned cam lobe and most unfavorably positioned cam lobes have practically uniform hardness, usually of about Rockwell C 60 although in different camshafts this may vary between 58-62, whereas, by the conventional method, the hardnesses of these lobes on the same camshaft were Rockwell C 57 and Rockwell C 50-52, respectively. The result is a greatly extended useful life for the camshaft.

The invention is practiced by forming drag and cope patterns like those illustrated at 50 and 52, of a matching nature, to form cooperative drag and cope members of the mold. The pattern has special thin projections that form thin ravines in the mold members, particularly in the cavities that form the nose zones of the cam lobes. Referring to FIGS. 5 and 6, drag-forming pattern 50 includes a support body 15 of any suitable material, having a surface forming a junction plane 17a with projections therefrom including a partial shaft cavity-forming projections 12a, partial bearing journal cavity-forming projections 14a at spaced intervals therealong, and partial cam lobe cavity-forming projections 18a. The cope forming pattern 52 likewise includes a suitable support 53 having a surface forming a juncture plane 16b, and projecting therefrom a partial shaft cavity-forming projections 12b, bearing journal cavity-forming projections 14b, and cam lobe cavity-forming projections 18b. Also protruding from this pattern is a riser forming projecting 54 at the gate end and a riser forming projection 56 of conventional type at the opposite end.

These pattern members also include the conventional type of pocket-forming blocks 20 on both pattern members, and projection forming pockets 22 on both members, to form corresponding pockets and projections in the mold material adjacent the noses of the cam lobes. This is done to prevent formation of small mold portions under the nose, and which would break off when the pattern is separated from the mold material. This is commonly known in the art.

The pattern members are distinctive in having a plurality of thin integral projections extending from the nose zones of the cam lobe cavity-forming projections 18a and 18b. Such projections can be seen most clearly in FIGS. 7 and 8. One of these projections is formed for each nose zone of the cam lobe forming members in the patterns. Because the orientation of the cam lobes on the camshaft casting to be formed are oriented at varying degrees around the circumference of the shaft, half of the partial projections that form the nose zone of the camshaft will be found on the cope forming pattern, and half will be found on the drag forming pattern.

These thin projections are located as close to the actual nose of the nose zones as possible, with some being necessarily slightly offset from the nose due to the position of the elements 20 on that particular cam lobe. All projections are oriented either normal to the juncture planes 17a and 17b of the pattern members, or coplanar therewith, or parallel thereto when occurring adjacent a pocket member.

Specifically, referring to FIGS. 7 and 8, FIG. 7 illustrates three such projections on the cope forming 52, all of these being shown in one of the preferred forms of the invention as thin fins having a width extending substantially the width of the cam lobe, and aligned axially of the camshaft casting. The first fin illustrated, F1, is oriented normal to juncture plane 17b, and is on a cam lobe which also includes a pocket forming block 20. Since the nose of this particular cam lobe is above the plane of the upper surface of pocket forming member 20, the fin can project directly from the nose, and protrudes upwardly normal to plane 17b. In the adjacent cam lobe however, the fin F2 lies directly upon the pocket forming projection 20 because the nose of this projection is substantially aligned with member 20, so that the fin is oriented parallel to plane 17b, elevated therefrom by the thickness of member 20, in order for it to be as close to the nose as possible. The third fin F3 illustrated in FIG. 7 projects directly upwardly from the vertically oriented nose of this cam lobe, thereby being perpendicular to plane 17b. The two remaining partial cam lobe cavityforming projections between the partial journal cavityforming projections 18b form the heel portions of the cavities and therefore do not have fins on them. Their exact counterpart in the drag forming pattern have the fins.

Referring now ot FIG. 8, the two cam lobe cavityforming projections there illustrated include one having a fin F4 which lies directly on the juncture plane 17a, and therefore substantially coplanar therewith, while the second fin F5 there illustrated is on a cam lobe cavityforming projection that has the nose slightly tilted from the vertical, with the fin directed normal to the plane of surface 17a.

These two pattern members 50 and 52 are employed to make the drag and cope members of the mold. The actual mold may be made of any known type mold material or the equivalent, including green sand materials, shell mold materials, permanent mold materials, furfural mold materials, carbon dioxide mold materials, or the like. When the two separate mold members are formed from these patterns, they are placed in matching mating relationship so that the lower cavity formed includes a shaft forming cavity, a plurality of the journal forming cavities, and a plurality of the cam lobe forming cavities. Each of the cam lobe forming cavities includes a ravine which is thin and projects either normal to, coplanar with, or parallel to the juncture plane of the cope and drag.

When the mold is thus formed, molten hardenable iron is poured into the gate and hence into one end of the elongated cavity. As it fills the mold, the molten metal flowing into the thin ravines forms fins which are almost instantly solidified into chill-throwing members metallurgically composed of white metal. These white metal members throw a chill back into the nose zones, including the nose and the adjacent ramp portions, causing practically uniform formation and concentration of acicular carbide in these nose zones. This results in hardness of the several cam lobes of practically uniform amounts, regardless of Where the cam lobe is positioned on the shaft, regardless of how close to the gate the particular cam lobes may be, regardless of whether the cam lobes are adjacent or not adjacent the large metal masses of the bearing journals being formed, and regardless of whether the nose portions of the cam lobes are positioned in the cope or the drag. The result is a highly advantageous cam shaft casting without any soft cam lobe nose Zones.

Within the broadest aspects of this invention, it is conceivable that this technique may be applied to only a selected number of the cam lobes in the camshaft, since it can be applied to the weaker sister cam lobe members on the shaft, thereby giving improved results over the prior art techniques. In the preferred form however, all of the cam lobes have such projections to obtain practically uniform hardness results over the length of the cam shaft.

It is also conceivable that the specific form of the fin projection may be modified somewhat as illustrated by the modified form in FIGS. 9 through 12.

More specifically, the invention has been explained with respect to the fin structure F illustrated in FIG.- 9 on the cam lobe, such fin extending substantially the width of the cam lobe and oriented lengthwise of the shaft, its base being as close as possible to the actual nose of the nose zone of the cam lobe and its structure being outwardly convergent. A lesser preferred form illustrated in FIG. 10 includes a plurality of tapered projection pins aligned generally along the width of the nose zone of the cam lobe, and with their larger ends at the nose zone. The chill action of these pins is not as great as that of the fin in FIG. 9, and further, the pattern pins on the pattern members tend to be broken ofl more readily.

A second preferred form of the invention includes a plurality of transverse fins TF shown in FIGS. 11 and 12, each transverse fin extending over the nose and into the ramp portions of the cam lobe, and a plurality of them being aligned side by side across the cam lobe Width, with the orientation of each being transverse to the camshaft axis.

It is conceivable that certain other variations in the details of construction may be modified within the concept presented, to obtain the improved results taught. Hence, the invention is intended to be limited only by the scope of the appended claims, and the reasonably equivalent structures to those defined therein.

I claim:

1. A method of founding a camshaft including the steps of (a) forming a mold composed of a cope, and a matching drag interfitting with said cope on a junction plane; said cope and drag together forming an elongated shaft-forming cavity, a plurality of spaced, bearing journal-forming cavities, and a plurality of cam lobeforming cavities, and said mold having a gate into one end of said shaft-forming cavity and (b) pouring molten hardenable iron into said mold through said gate; the improvement comprising: forming into said mold in the nose zone of at least one of the cam lobe-forming cavities near said gate, a thin, metal receiving ravine projecting from the nose forming portion of said cavity in a direction either parallel to, coplanar with, or normal to said junction plane; pouring molten hardenable iron into said mold through said gate, causing metal in said ravine to solidify almost instantly into white metal that throws a solidifying chill into the adjacent cam lobe nose zone being formed and causes concentrated acicular carbide formation therein, thereby overcoming the adverse factors of partial mold preheating with fiowing incoming metal, of heat retention adjacent to bearing journals, and of slower cooling action in the cope.

2. A method of founding a camshaft having both increased carn lobe nose and ramp hardness, and also generally uniform hardness in all of the cam lobe noses and ramps over the length of the shaft, including the steps of (a) forming a mold composed of a cope, and a matching drag interfitting with said cope on a junction plane; said cope and drag together forming an elongated shaftforming cavity, a plurality of spaced bearing journalforming cavities, and a plurality of cam lobe-forming cavities, and said mold having a gate into one end of said shaft-forming cavity, and (b) pouring molten hardenable iron into said mold through said gate, the improvement comprising: forming into a plurality of thin, metal receiving ravines, at least one projecting from the nose zone of each cam lobe-forming cavity, part of said ravines being in said cope and part in said drag; pouring molten hardenable iron into said mold through said gate, causing metal in said ravines to solidify almost instantly into white metal projections that throw a chill back into the adjacent cam lobe nose zones being formed and cause like concentrated acicular carbide formation in all of said nose zones, thereby overcoming the adverse factors of partial mold preheating with flowing incoming metal, of heat retention adjacent to bearing journals, and of slower cooling action in the cope, and thereby causing generally uniform and improved metallurgical structure in all of the cam lobe noses and ramps.

3. The method in claim 2 wherein said thin ravines all project parallel to, coplanar with, or normal to said junction plane.

4. The method in claim 2 wherein said plurality of ravines are formed as a plurality of spaced fin-forming ravines on each cam lobe cavity, each ravine extending over the nose forming portion into the ramp forming portions of the mold.

5. The method of claim 2 wherein said ravines are formed as fin-forming ravines, each one extending substantially over the width of a nose forming zone of the mold.

6. The method in claim 2 wherein said ravines are shaped like pins.

7. A novel camshaft casting having a plurality of cam lobes and spaced bearing journals, said cam lobes all along the length of the shaft having generally uniform hardness and acicular carbide concentration in the plurality of cam lobe nose zones, and having thin integral projections of white iron protruding away from said cam lobe nose zones, to be removed during grinding.

8. The camshaft casting in claim 7 wherein said projections comprise a thin fin extending substantially the width of each lobe nose.

9. The camshaft casting in claim 8 wherein said fins have an outwardly convergent cross section.

10. The camshaft in claim 7 wherein said projections comprise a plurality of adjacent pins on each lobe nose.

11. The camshaft in claim 7 wherein said projections comprise a plurality of adjacent pins across the width of each lobe, each extending from the nose and adjacent ramp portions.

12. The camshaft in claim 7 wherein said projections extend only perpendicular, parallel or coplanar with respect to each other.

13. A mold pattern for founding camshafts comprising a cope forming member and a drag forming member, each having a juncture plane with projections therefrom forming partial shaft, bearing journal, and eccentric cam lobe patterns capable of forming cooperative cope and drag mold members that will have complete shaft, bearing journal, and eccentric cam lobe forming cavities therein; and said partial cam lobe forming projections all having thin integral projections extending from the nose regions thereof, some from said drag forming member and some from said cope forming member, with such projections being only normal to, parallel to, or generally coplanar with the respective juncture plane of the forming member on which it is located.

14. The mold pattern in claim 13 wherein said projections comprise thin tapered fins.

15. The mold pattern in claim 13 wherein said projections comprise tapered pins.

References Cited UNITED STATES PATENTS 3,122,822 3/1964 Kueny 29156.7

J. SPENCER OVERHOLSER, Primary Examiner.

V. K. RISING, Assistant Examiner.

US. Cl. X.R. 

